A building is so much more than just a roof over your head. Because buildings use 40% of all of our energy, they represent a huge opportunity: Redesign how our buildings work and we could go a long way toward solving our emissions issues. We saw the start of that this year, with the most energy efficient office ever opening in Seattle and a building in Germany that gets its power from algae that live in its walls.

But buildings are also where we spend most of our time, so they should make us happy to be inside them. And so projects like the giant skyscraper in Shanghai are incredibly important. It's filled with parks and open to the public, in an attempt to get people spending more time with nature. At the other end of the market, there's the $20,000 house designed initially for impoverished rural Alabamans. But the houses are so nice (and so cheap), they may soon hit the market for everyone.

The Bullitt Center is made from totally clean materials, has composting toilets, and catches enough rainwater to survive a 100-day drought. And it’s 100% solar-powered, in a city not known for its sunny days.